Golf ball composition

Abstract

A golf ball, a golf ball core and a method for making a golf ball and a golf ball core, using an admixture of polybutadiene, a zinc diacrylate cross-linker, and a calcium oxide that is substantially free of zinc oxide. When zinc oxide, typically used in golf ball cores, is eliminated or at least substantially reduced from a golf ball core composition, and calcium oxide is added, the golf balls and golf ball cores formed from such an admixture exhibit reduced PGA compression when compared to cores and balls containing zinc oxide, while maintaining the initial velocity of the standard higher compression cores and balls.

I claim: 
     
       1. A method of manufacturing a low PGA compression golf ball, which comprises: forming a first mixture comprising polybutadiene, calcium oxide in an amount of about 0.1 to 15 parts per 100 parts of polybutadiene; and, from about 20 to 50 parts per 100 of a metal salt of a material selected from the group consisting of diacrylates, dimethacrylates, and monomethacrylates;   combining at least one free radical initiator with the first mixture to form a golf ball core composition; and   forming a golf ball core from the composition.   
     
     
       2. The method of claim 1 further comprising combining the polybutadiene and the metal salt prior to adding the calcium oxide to form the first mixture. 
     
     
       3. The method of claim 1, further comprising forming the first mixture with the calcium oxide in an amount of about 1 to 10 parts per 100 parts of the polybutadiene. 
     
     
       4. The method of claim 1, further comprising forming the first mixture with the calcium oxide in an amount of about 1.25 to 5 parts per 100 parts of the polybutadiene. 
     
     
       5. The method of claim 1, further comprising forming the first mixture with a polybutadiene having a cis-1,4-polybutadiene content of at least about 90%. 
     
     
       6. The method of claim 1, further comprising molding the golf ball core composition into a unitary golf ball. 
     
     
       7. The method of claim 1 which further comprises selecting at least one peroxide for use as the free radical initiator. 
     
     
       8. A method of manufacturing a low PGA compression golf ball core comprising the steps of: forming a first mixture substantially free of zinc oxide, said first mixture comprising polybutadiene, zinc diacrylate in an amount of about 20 to about 50 parts per 100 parts of polybutadiene, and calcium oxide in an amount of about 0.1 to about 15 parts per 100 parts of polybutadiene;   allowing the temperature of the first mixture to rise to a range at which a free radical initiator added thereto will form free radicals;   combining a free radical initiator with the first mixture to form a golf ball core composition; and   forming a golf ball core from the composition.   
     
     
       9. The method of claim 8 which further comprises selecting at least one peroxide for use as the free radical initiator. 
     
     
       10. The method of claim 9, wherein the free radical initiator is added at a temperature ranging between about 80° and 200° F. 
     
     
       11. A golf ball core, produced according to the method of claim 8. 
     
     
       12. A golf ball comprising a core formed according to claim 8. 
     
     
       13. A low PGA compression golf ball comprising a cover and a core, wherein the core is formed from a mixture, substantially free of zinc oxide, said mixture comprising polybutadiene, a metal salt of a material selected from the group consisting of diacrylates, dimethacrylates, and monomethacrylates, and calcium oxide, wherein the amount of the calcium oxide is sufficient to reduce the compression of a golf ball by at least about 2 PGA compression points compared to a core consisting of the same mixture wherein zinc oxide is substituted in place of the calcium oxide. 
     
     
       14. The golf ball of claim 13, wherein the amount of calcium oxide in said mixture is from about 0.1 to 15 parts per 100 parts of polybutadiene. 
     
     
       15. The golf ball of claim 13, wherein the amount of calcium oxide in said mixture is from about 1 to about 10 parts per 100 parts of polybutadiene. 
     
     
       16. The golf ball of claim 13, wherein the amount of calcium oxide in said mixture is from about 1.25 to 5 parts per 100 parts of polybutadiene. 
     
     
       17. The golf ball of claim 13, wherein the polybutadiene has a cis-1,4-polybutadiene content of at least about 90%. 
     
     
       18. The golf ball of claim 13, wherein the polybutadiene has a cis-1,4-polybutadiene content of at least about 96%. 
     
     
       19. The golf ball of claim 13, wherein the amount of the metal salt in said mixture is about 20 to 50 parts per 100 parts of polybutadiene. 
     
     
       20. The golf ball of claim 19, wherein the metal salt is zinc diacrylate. 
     
     
       21. The golf ball of claim 13, wherein the core further comprises a filler selected from the group consisting of barium sulfate, regrind, limestone, and mixtures thereof. 
     
     
       22. A low PGA compression golf ball core composition substantially free of zinc oxide, said composition comprising polybutadiene, a metal salt of a material selected from the group consisting of diacrylates, dimethacrylates, and monomethacrylates and calcium oxide in an amount of about 0.1 to 15 parts per 100 parts of said polybutadiene. 
     
     
       23. The golf ball core composition of claim 22, wherein the amount of calcium oxide, in said composition is from about 1 to about 10 parts per 100 parts of said polybutadiene. 
     
     
       24. The golf ball core composition of claim 22, wherein the amount of calcium oxide in said composition is from about 1.25 to about 5 parts per 100 parts of said polybutadiene. 
     
     
       25. The golf ball core composition of claim 22, wherein the polybutadiene has a cis-1,4-polybutadiene content of at least about 90%. 
     
     
       26. The golf ball core composition of claim 22, wherein the metal salt is zinc diacrylate.